While these shark encounters might look like fun, George Burgess, program director at the Florida Program for Shark Research, believes this kind of activity would be detrimental to the animals.

"Sharks are aquatic animals - they're not made to be out of the water, anymore than we're made to be living under the water," Burgess told The Dodo. "Taking them out of their natural habitat is not good for them. They have to breathe through the inhalation of water into their gills, so if you take them out of the water, you're starting the process of suffocation."

Heather Rally, a wildlife veterinarian with the PETA Foundation, tends to agree.

"Sharks cannot breathe out of the water and, on top of that, their blood doesn't carry oxygen that well," Rally told The Dodo. "So that means they could easily suffocate if they're removed from the water for any period of time, especially if it's repeatedly. They actually have muscles that run water over their gills all the time, and that's how they extract oxygen from the water. So they can't actually physically do that from the air."

But it's not just suffocation that these sharks would be subjected to. Their bodies could also be injured when lifted out of the water, according to Rally.

"Their organs, their musculature, their skin - everything is susceptible to damage under the force of gravity, and with manipulation from human hands, especially untrained hands like members of the public who are manipulating them for photo ops," Rally said.

The Dodo could not reach Playa Tiburon for comment. But a recent petition claims that "many tour boats and catamarans take hundreds of tourists to this famous dock daily" to swim with the sharks. It also notes that the tourists can swim inside the sea pen with the sharks for free, but have to pay $20 for a photograph.

Living in a small sea pen would be stressful enough - but encountering multiple people each day would make it even worsel, Rally explained.

"Sharks have highly specialized sensory systems that allow them to detect tiny vibrations in the water, electrical impulses and even odors from quite a great distance away," Rally said. "These sensory systems aren't just on their noses and their heads - they're all along the shark's entire body. So you can imagine how that would be a great advantage to a shark out in the ocean, but a disadvantage in a tank, especially when being manipulated and chased by tourists."

While nurse sharks are docile, gentle creatures, Burgess also worries that, sooner or later, they might get agitated enough to bite someone. In the photographs, it appears a "keeper" has the job of holding the shark's head, perhaps to prevent injury. But Burgess doesn't think this is good enough.

"Although it is a very docile animal, it has its limits," Burgess said. "If it gets pissed off enough to bite you, it is very bulldog-like, and won't let go ... and then there will be a big headline about a shark attack in Cancun."

The best solution for the sharks is for them to be released, according to Rally.

"This restaurant needs to end their shark exploitation program and release these innocent animals back into the ocean where they will be free from harassment and contribute, as they naturally do, to the conservation of their ocean ecosystem," Rally said.